间伐强度对杉木人工林材种结构的影响

Effect of thinning intensity on timber structure of Chinese fir plantation

以福建省南平市洋口国有林场16年生间伐后3 a内的杉木人工林为研究对象,设置强度间伐(HIT)、弱度间伐(LIT)和未间伐[对照(CK)]3个间伐梯度,探讨间伐强度对杉木人工林生长、干形以及材种结构动态变化规律的影响.结果表明:(1)间伐能促使保留木胸径和树高增长;(2)间伐能够影响林木的胸高形数和径高比,随着间伐强度的增大胸高形数表现为CK>LIT>HIT,径高比表现为HIT>LIT>CK;(3)林木平均单株材积随间伐强度的增大表现为HIT>LIT>CK,且间伐强度越大,增长越明显;(4)在观测年限内,林分蓄积量随间伐强度的增大呈递减趋势,而林分蓄积定期增长量和增长率随间伐强度的增大而增大,活立木规格材出材率随间伐强度的增大而增大,且受间伐影响显著;(5)间伐能够影响林分的材种结构,促使小中径材更早进入下一径阶.在立地质量(SI)≥22及0≤间伐强度≤35%的条件下,间伐强度越大,越适宜大径材培育.

To study the impact of thinning intensity on the growth,form,and timber assortment structure of Chinese fir plantation,3 thinning intensities,heavy thinning(HIT),light thinning(LIT)and non-thinning(CK),were implemented for 3 consecutive years on 16-year-old Chinese fir plantation in Yangkou State-owned Forest Farm of Nanping City,Fujian Province.The results showed that(1)the growth of diameter at breast height and tree height were lifted after thinning.(2)Breast height form factor of stands from different treatments followed the order of CK>LIT>HIT,while diameter-height ratio followed the opposite order of HIT>LIT>CK.(3)HIT resulted in the highest average individual volume,and was followed by LIT;the greater thinning intensity implemented,the more obvious growth in individual volume it achieved.(4)Stand bulk volumes decreased while yearly growths and growth rates of stand volume grew with the increased thinning intensities.The yield of dimension lumber from standing forest stock went up when thinning intensity increased,and was significantly affected by thinning intensity.(5)Thinning altered the timber assortment structure of the stand,and upscaled timbers in small and middle-diameter to higher diameter classes in advance.To summarize,greater thinning intensity(≤35%)is contributed to the cultivation of large-diameter timber for Chinese fir plantation with site quality over 22.